Author Information: Mary Babitz is the Vice President of Cascade TEK, an A2LA accredited environmental product testing laboratory. Thermal shock testing is one of many tests carried out in Cascade TEK’s two laboratories. In addition to product testing, they also manufacture high quality vacuum and laboratory ovens used for drying, curing and vacuum bake-out applications. Read more interesting facts about the science of product testing on their blog.
Thermal shock testing is performed to determine the ability of parts to withstand sudden changes in temperature. Thermal shock chambers rapidly move products between ”hot” and “cold” temperature zones many times to see the effects of thermal expansion and contraction (expansion with heat, contraction with cold). A thermal shock test generally means the transition from temperature extremes is done in five minutes or less.
There are a number of thermal shock testing profiles. Originating in the 1950’s, MIL-STD-202, Method 107 is generally understood to be the first of the thermal shock test profiles and the basis for the thermal shock test specifications of today. Some test specs specify using an “air to air” thermal shock chamber, while some specify using a “liquid to liquid” thermal shock chamber. MIL-STD 202, Method 107 allows for testing in both air to air and liquid to liquid chambers.
What are the differences?
Liquid to Liquid Shock Chambers have separately controlled hot and cold baths in an inert liquid (typically Galden). The liquid provides an excellent heat exchange rate, allowing the item under test to be moved very rapidly between temperature extremes and providing an immediate product temperature change. This is the key benefit. The liquid used in liquid thermal shock testing also does not coat the product or conduct electricity. The fluid, however, is very expensive and leakage and evaporation are always a possibility. Liquid to liquid chambers are also not as readily available as air to air chambers and are generally more expensive. Continue reading